tailieunhanh - Báo cáo khoa học: "Ambiguity resolution in a reductionistic parser"

W e are concerned with dependencyoriented morphosyntactic parsing of running text. While a parsing grammar should avoid introducing structurally unresolvable distinctions in order to optimise on the accuracy of the parser, it also is beneficial for the g r a m m a r i a n to have as expressive a structural representation available as possible. | Ambiguity resolution in a reductionistic parser Atro Voutilainen Pasi Tapanainen Research Unit for Computational Linguistics . Box 4 Keskuskatu 8 FIN-00014 University of Helsinki Finland Abstract We are concerned with dependency-oriented morphosyntactic parsing of running text. While a parsing grammar should avoid introducing structurally unresolvable distinctions in order to optimise on the accuracy of the parser it also is beneficial for the grammarian to have as expressive a structural representation available as possible. In a reductionistic parsing system this policy may result in considerable ambiguity in the input however even massive ambiguity can be tackled efficiently with an accurate parsing description and effective parsing technology. 1 Introduction In this paper we are concerned with grammar-based surface-syntactic analysis of running text. Morphological and syntactic analysis is here based on the use of tags that express surface-syntactic relations between functional categories such as Subject Modifier Main verb etc. consider the following simple example I PRON QSUBJECT see V PRES OMAINVERB a ART CDET H bird H SOBJECT FULLSTOP The development of ENGCG was supported by TEKES the Finnish Technological Development Center and a part of the work on Finite-state syntax has been supported by the Academy of Finland. In this type of analysis each word gets a mor-phosyntactic analysis1. The present work is closely connected with two parsing formalisms Constraint Grammar Karlsson 1990 Karlsson et al. 1991 Voutilainen et al. 1992 Karlsson el al. 1993 and Finite-state syntax as advocated by Koskenniemi 1990 Tapanai-nen 1991 Koskenniemi et al. 1992 . The Constraint Grammar parser of English is a sequential modular system that assigns a shallow surface-true dependency-oriented functional analysis on running text annotating each word with morphological and syntactic tags. The finite-state parser assigns a similar type of analysis but it operates on all levels of